100 Gb/s Silicon Photonic WDM Transmitter with Misalignment-Tolerant Surface-Normal Optical Interfaces
Authors: Huang, BJ; Zhang, ZY; Zhang, Z; Cheng, CT; Zhang, H; Zhang, HJ; Chen, HD
Volume: 10 Issue: 5 Published: MAY 2019 Language: English Document type: Article
A 4 x 25 Gb/s ultrawide misalignment tolerance wavelength-division-multiplex (WDM) transmitter based on novel bidirectional vertical grating coupler has been demonstrated on complementary metal-oxide-semiconductor (CMOS)-compatible silicon-on-insulator (SOI) platform. Simulations indicate the bidirectional grating coupler (BGC) is widely misalignment tolerant, with an excess coupling loss of only 0.55 dB within +/- 3 m fiber misalignment range. Measurement shows the excess coupling loss of the BGC is only 0.7 dB within a +/- 2 m fiber misalignment range. The bidirectional grating structure not only functions as an optical coupler, but also acts as a beam splitter. By using the bidirectional grating coupler, the silicon optical modulator shows low insertion loss and large misalignment tolerance. The eye diagrams of the modulator at 25 Gb/s don't show any obvious deterioration within the waveguide-direction fiber misalignment ranger of +/- 2 m, and still open clearly when the misalignment offset is as large as +/- 4 m.